WO2020010609A1

WO2020010609A1 - Power supply circuit, controlling method and electric equipment

Info

Publication number: WO2020010609A1
Application number: PCT/CN2018/095617
Authority: WO
Inventors: Qiuxiang MAO
Original assignee: Tridonic Gmbh & Co Kg
Priority date: 2018-07-13
Filing date: 2018-07-13
Publication date: 2020-01-16
Also published as: CN112119578B; CN112119578A; EP3799674A4; EP3799674B1; EP3799674A1

Abstract

A power supply circuit, a controlling method and an electric equipment are provided. The power supply circuit includes : a voltage convertor circuit, configured to convert an input voltage into an output voltage, the voltage convertor circuit having a primary side and a secondary side, the primary side having at least one switch unit which controls the primary side to rectify the input voltage, the secondary side having at least two rectifying diodes, which being used to rectify voltage coupled from the primary side; a controller, configured to generate a controlling signal to control the switch unit; and a voltage generator, configured to be coupled to the primary side, being used to generate a voltage, and provide the voltage to a power supply terminal of the controller, when the at least two rectifying diodes being normal, the voltage provided to the controller being an operating voltage of the controller, and the controller generates the controlling signal by being provided with the operating voltage; when one of the at least two rectifying diodes being open, the voltage provided to the controller being shutdown voltage, and the controller stops generating the controlling signal by being provided with the shutdown voltage. Therefore, the rectifying diode will not get hot, the cost is low and the reliability is high.

Description

POWER SUPPLY CIRCUIT, CONTROLLING METHOD AND ELECTRIC EQUIPMENT

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of voltage conversion, and more particularly, to a power supply circuit, a controlling method and an electric equipment.

BACKGROUND

This section introduces aspects that may facilitate better understanding of the present disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the related art.

In the field of power conversion, a switching element and a transformer may be included in a power supply circuit. The switching element may be controlled to be switched on or off, a voltage generated in a primary wind of the transformer changes, and an induced voltage is generated in a secondary wind of the transformer. The voltage generated in the secondary wind will be rectified and filtered, so as to generate an output voltage.

Therefore, the input voltage is converted into the output voltage. The output voltage may change according to the switching frequency and duty ratio of a controlling signal that controls the switching element.

The controlling signal may be generated and provide by a controller. The controller may be powered by an auxiliary winding that is coupled with the primary winding.

Fig. 1 is a diagram of a power supply circuit. As shown in Fig. 1, the power supply circuit 10 includes a switching element S, a transformer T, at least two rectifying diode D1 and D2, an auxiliary winding L3, and a controller 100.

The switching element S is controlled by the controller 100. The transformer T includes a primary winding L1 and a secondary winding L2. The auxiliary winding L3 is coupled to the primary winding L1, and voltage will be generated at one terminal of the auxiliary winding L3. The controller 100 is powered by the voltage generated at the terminal of the auxiliary winding L3.

The primary side 10a of the power supply circuit 10 may have the topology of LLC resonant circuit, LC resonant circuit or PWM (Pulse Width Modulation) circuit.

The secondary side 10b of the power supply circuit 10 may include at least two rectifying diodes D1 and D2, which is used to rectifying voltage generated on the secondary winding L2. As shown in Fig. 1, the rectifying diodes D1 and D2 are contained in a half bridge rectifier. Capacitor C can be used to filter the output voltage V _out. However, in another example, the rectifying diodes D1 and D2 may be contained in a full bridge rectifier.

For the power supply circuit 10 in single fault test to get safety approval, one rectifying diode in D1 and D2 will be open, the other rectifying diode becomes very hot to exceed limit because more current flow through the other rectifying diode. When one rectifying diode is open, the power supply circuit 10 can still work, another diode will get hot and fail in safety test.

In related art, there are two solutions for solving the problem of one rectifying diode getting hot.

The first solution is to arrange additional diode in parallel with D1 or D2. Fig. 2 shows one solution. As shown in Fig. 2, at the secondary side of the power supply circuit 10, diode D11 is arranged in parallel with D1, diode D21 is arranged in parallel with D2. When diode D1 or D2 is open, the diode D11 or D21 which is in parallel with diode D1 or D2 can still work. Therefore, the rectifying diode will not get hot.

The second solution is to use low withstanding voltage Schottky diodes as the rectifying diodes. When one Schottky diode is open, another Schottky diode will breakdown by high reverse voltage.

SUMMARY

Inventors of this disclosure found the two solutions above mentioned have their respective drawbacks: for the first solution, the additional diodes of D11 and D21 will bring additional cost; for the second solution, Schottky diode will bring higher cost, furthermore, when load condition changes, the second solution will not work well, thus the reliability is low.

In general, embodiments of the present disclosure provide a power supply circuit, a controlling method and an electric equipment. In the embodiments, when one of the at least two rectifying diodes is open, the voltage provided to the controller will be shutdown voltage, so that the controller stops generating a controlling signal and the power supply circuit stops work. Therefore, the rectifying diode will not get hot, the cost is low and the reliability is high.

In a first aspect, a power supply circuit is provided, the power supply circuit includes: a voltage convertor circuit, configured to convert an input voltage into an output voltage, the voltage convertor circuit having a primary side and a secondary side, the primary side having at least one switch unit which controls the primary side to rectify the input voltage, the secondary side having at least two rectifying diodes, which being used to rectify voltage coupled from the primary side; a controller, configured to generate a controlling signal to control the switch unit; and a voltage generator, configured to be coupled to the primary side, being used to generate a voltage, and provide the voltage to a power supply terminal of the controller, when the at least two rectifying diodes being normal, the voltage provided to the controller being an operating voltage of the controller, and the controller generates the controlling signal by being provided with the operating voltage; when one of the at least two rectifying diodes being open, the voltage provided to the controller being shutdown voltage, and the controller stops generating the controlling signal by being provided with the shutdown voltage.

In an embodiment, the voltage generator includes:

an auxiliary winding, arranged on the primary side, and arranged between a first node and a second node, the auxiliary winding couples to a primary winding of the primary side of the voltage convertor circuit; a first diode (D32) , arranged in a first branch connecting the first node and the power supply terminal of the controller; a second diode (D34) , arranged in a second branch connecting the first node and the power supply terminal of the controller; and a Zener diode (Z31) , arranged in the second branch, the operating voltage is provided through the first branch, the shutdown voltage is provided through the second branch.

In an embodiment, the cathode of the second diode is coupled to the first node, the anode of the second diode is coupled to the anode of the Zener diode.

In an embodiment, the power supply circuit further comprises: a resistor, arranged in series with the second diode and the Zener diode in the second branch.

In an embodiment, the anode of the first diode is coupled to the first node.

In an embodiment, the second node is coupled to a ground potential.

In a second aspect, an electric equipment is provided. The electric equipment includes the power supply circuit according to any one of above embodiments.

In a third aspect, a controlling method of a power supply circuit is provided, the method includes: a voltage convertor circuit converting an input voltage into an output voltage, the voltage convertor circuit having a primary side and a secondary side, the primary side having at least one switch unit which controls the primary side to rectify the input voltage, the secondary side having at least two rectifying diodes, which being used to rectify voltage coupled from the primary side; a controller generating a controlling signal to control the switch unit; and a voltage generator generating a voltage, and providing the voltage to a power supply terminal of the controller, the voltage generator being configured to be coupled to the primary side, being used to when the at least two rectifying diodes being normal, the voltage provided to the controller being an operating voltage of the controller, and the controller generates the controlling signal by being provided with the operating voltage; when one of the at least two rectifying diodes being open, the voltage provided to the controller being shutdown voltage, and the controller stops generating the controlling signal by being provided with the shutdown voltage.

According to various embodiments of the present disclosure, when one of the at least two rectifying diodes is open, the voltage provided to the controller will be shutdown voltage, so that the controller stops generating a controlling signal and the power supply circuit stops work. Therefore, the rectifying diode will not get hot, the cost is low and the reliability is high.

In a further aspect, a lighting device driver is provided, comprising the power supply circuit according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and benefits of various embodiments of the disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements. The drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:

Fig. 1 is a diagram of a power supply circuit in related art;

Fig. 2 shows the first solution in related art;

Fig. 3 is a diagram of a power supply circuit in accordance with an embodiment of the present disclosure;

Fig. 4 is a diagram of the output voltage Vout when the power supply circuit is in normal operation;

Fig. 5 is a diagram of the output voltage Vout when one rectifying diode is open.

Fig. 6 is a flowchart of a controlling method 600 of the power supply circuit.

DETAILED DESCRIPTION

The present disclosure will now be discussed with reference to several example embodiments. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure.

As used herein, the terms “first” and “second” refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises, ” “comprising, ” “has, ” “having, ” “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on. ” The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” Other definitions, explicit and implicit, may be included below.

In the description and drawings, particular embodiments of the disclosure have been disclosed in detail as being indicative of some of the ways in which the principles of the disclosure may be employed, but it is understood that the disclosure is not limited correspondingly in scope. Rather, the disclosure includes all changes, modifications and equivalents coming within the spirit and terms of the appended claims.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

It should be emphasized that the term “includes/including” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. To facilitate illustrating and describing some parts of the disclosure, corresponding portions of the drawings may be exaggerated in size, e.g., made larger in relation to other parts than in an exemplary device actually made according to the disclosure. Elements and features depicted in one drawing or embodiment of the disclosure may be combined with elements and features depicted in one or more additional drawings or embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views and may be used to designate like or similar parts in more than one embodiment.

First aspect of embodiments

A power supply circuit is provided in a first embodiment.

Fig. 3 is a diagram of a power supply circuit in accordance with an embodiment of the present disclosure. As shown in Fig. 3, the power supply circuit 300 includes a voltage convertor circuit 301, a controller 302, and a voltage generator 303.

In the embodiment, the voltage convertor circuit 301 is configured to convert an input voltage Vin into an output voltage Vout. The voltage convertor circuit 301 may have a primary side 301a and a secondary side 301b. The voltage convertor circuit 301 may be also configured to provide a defined output current.

The power supply circuit 300 with the voltage convertor circuit 301 may form a part of a lighting device driver. A lighting device, e.g. one or more light emitting diodes (LEDs) , may be connected to the output voltage Vout. In an alternative embodiment a further driver circuit like a buck converter or buck-boost converter may be connected to the output voltage Vout and may be used to drive a lighting device. The output voltage Vout may be provided by output terminals in order to be able to connect a light device to the power supply circuit 300.

The voltage convertor circuit 301 may be also configured to provide a stable output voltage Vout at a defined output current. The output current may be defined depending on the intended use of LED as lighting device.

The primary side 301a has at least one switch unit Q3 which controls the primary side 301a to rectify the input voltage Vin. The secondary side 301b has at least two rectifying diodes D80 and D81, which are used to rectify voltage coupled from the primary side 301b.

In the embodiment, the controller 302 is configured to generate a controlling signal to control the switch unit Q3.

The voltage generator 303 is configured to be coupled to the primary side 301a. The voltage generator 303 is used to generate a voltage, and provide the voltage to a power supply terminal VDD (pin number 6) of the controller 302.

In the embodiment, when the at least two rectifying diodes D80 and D81 is normal, the voltage provided to the controller 302 is an operating voltage of the controller 302, and the controller 302 generates the controlling signal by being provided with the operating voltage.

In the embodiment, when one of the at least two rectifying diodes D80 and D81 is open, the voltage provided to the controller 302 is shutdown voltage, and the controller 302 stops generating the controlling signal by being provided with the shutdown voltage.

According to the embodiment, when one of the at least two rectifying diodes is open, the controller 302 stops generating the controlling signal and the power supply circuit 300 will stop work. Therefore, the rectifying diode will not get hot, the cost is low and the reliability is high.

In the embodiment, as shown in Fig. 3, the voltage convertor circuit 301 may further include a transformer T3, a primary winding T31-a is contained in the primary side 301a, and secondary windings T32-a and T32-b are contained in the secondary side 301b.

The switch unit Q3 may include at least two switch elements Q30 and Q31, the at least two switch elements maybe MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or BJT (Bipolar Junction Transistor) .

In the embodiment, other elements contained in the primary side 301a are not shown in Fig. 3, these elements may include a capacitor C30, two diodes D30 and D31, and an inductor L30. The function of these elements can be referred to related arts.

The primary side 301a of the voltage convertor circuit 301 may have the topology of a half bridge circuit with transformer T3, e.g. LLC resonant circuit, LC resonant circuit or PWM (Pulse Width Modulation) circuit. However, the embodiment is not limited there to, the primary side 301a may have other kind of topology.

The output voltage or output current may change according to the switching frequency and/or duty ratio of a controlling signal provided by controller 302 that controls the switching elements Q30 and Q31.

In the embodiment, the secondary side 301b of the voltage convertor circuit 301 may include a half bridge rectifier. The at least two rectifying diodes D80 and D81 may be contained in the half bridge rectifier. However, the embodiment is not limited there to, the secondary side 301b of the voltage convertor circuit 301 may include a full bridge rectifier, and the at least two rectifying diodes D80 and D81 may be contained in the full bridge rectifier.

In the embodiment, the secondary side 301b of the voltage convertor circuit 301 may further include capacitors C80～C83, and resistors R80～R83. The function of these elements can be referred to related arts.

In the embodiment, shown in Fig. 3, the voltage generator 303 may include: an auxiliary winding T31-b, a first diode D32, a second diode D34 and a Zener diode Z31.

In the embodiment, the auxiliary winding T31-b may be arranged on the primary side 301a, and arranged between a first node N1 and a second node N2. The auxiliary winding T31-b couples to the primary winding T31-a of the primary side 301a of the voltage convertor circuit 301.

The first diode D32 is arranged in a first branch B1 connecting the first node N1 and the power supply terminal Vdd of the controller 302.

The second diode D34 is arranged in a second branch B2 connecting the first node N1 and the power supply terminal Vdd of the controller 302.

The Zener diode Z31 is arranged in the second branch B2.

In the embodiment, the operating voltage is provided through the first branch B1, and the shutdown voltage is provided through the second branch B2.

As shown in Fig. 3, the cathode of the second diode D34 is coupled to the first node N1, the anode of the second diode D34 is coupled to the anode of the Zener diode Z31.

As shown in Fig. 3, the power supply circuit further includes a resistor R55. The resistor R55 is arranged in series with the second diode D34 and the Zener diode Z31 in the second branch B2.

As shown in Fig. 3, the anode of the first diode D32 is coupled to the first node N1, and the cathode of the first diode D32 is coupled to the power supply terminal Vdd of the controller 302.

As shown in Fig. 3, the second node N2 may be coupled to a ground potential.

Fig. 4 is a diagram of the output voltage Vout when the power supply circuit is in normal operation. Fig. 5 is a diagram of the output voltage Vout when one rectifying diode is open.

When the at least two rectifying diodes D80 and D81 are normal, the power supply circuit 300 is working in a normal operation. As shown in Fig. 4, the output voltage Vout is symmetrical in a lower level, for example, the maximum Vout in reverse direction is -9.33V, the maximum Vout in forward direction is 8.92V.

The operation voltage corresponding to the Vout in forward direction can be generated at the first node N1 of the auxiliary winding T31-b. The operation voltage can be in forward direction, and the first diode D32 conducts, so that the operation voltage can be provided to the power supply terminal Vdd through the first branch B1.

Besides, when the power supply circuit 300 is working in a normal operation, a voltage corresponding to the Vout in reverse direction can be generated at the first node N1 of the auxiliary winding T31-b. This reversed voltage is not higher than the breakdown voltage of the Zener diode Z31, hence, the reversed voltage will be blocked by the Zener diode Z31 and will not be provided to the power supply terminal Vdd.

When one of the at least two rectifying diodes D80 and D81 is open, for example D80 is open, the power supply circuit 300 is working in an abnormal operation. As shown in Fig. 5, the output voltage Vout is unsymmetrical, and the output voltage Vout in reverse direction is much higher than that is shown in Fig. 4. For example, the maximum Vout in reverse direction of Fig. 5 is -53.5V, the maximum Vout in forward direction of Fig. 5 is 14.45V.

According to Fig. 5, the shutdown voltage corresponding to the Vout in reverse direction can be generated at the first node N1 of the auxiliary winding T31-b. The shutdown voltage can be in reverse direction. The maximum Vout in reverse direction is very high, the reversed voltage at the first node N1 can be higher than the breakdown voltage of the Zener diode Z31, and the Zener diode Z31 can be in a state of breakdown.

Therefore, the second diode D34 conducts, the power supply terminal Vdd will discharge through the resistor R55, the Zener diode Z31, and the second diode D34. In another word, the reversed voltage generated at the first node N1 can be provided to the power supply terminal Vdd through the second branch B2.

In the embodiment, as shown in Fig. 3, the controller 302 may have: terminal Vs (pin number 1) , terminal Comp (pin number 2) , terminal Tx1 (pin number 3) , terminal Tx2 (pin number 4) , terminal Rc (pin number 5) , terminal GND (pin number 7) , and terminal Cs (pin number 8) .

The terminal Vs is inputted a voltage signal corresponding to a voltage at the auxiliary winding. The voltage signal can be generated by a network including diode D33, capacitors C35, C40, C39, and resistors R49, R44, R46.

The terminal Cs is inputted a current signal corresponding to a current on the primary winding. The current signal can be generated by a network including resistors R32～R36, J3, and capacitor C35.

The terminal Rc is coupled to an external network including resistors C38, and capacitor R40. The terminal Rc is used to set the minimum switching frequency of the controlling signal.

The terminal Tx1 and Tx2 may output the controlling signal to the switch unit Q3, for example, the terminal Tx1 and Tx2 may output first controlling signal SN1 and second controlling signal SN2, respectively. The terminal Tx1 and Tx2 may be coupled to two terminals of a primary winding of a control transformer, and secondary windings of the control transformer will be used to turn the switch elements Q30 and Q31 on or off.

As shown in Fig. 3, functions of other elements listed in Fig. 3 can be referred to the related art.

In the embodiment, PSR (Primary Side Regulation) can be performed by the controller 302 in the power supply circuit 300.

According to the embodiment, when one of the at least two rectifying diodes at the secondary side is open, the voltage in reverse direction will be provided to the power supply terminal of the controller, and the controller stops generating the controlling signal and the power supply circuit will stop work. Therefore, the rectifying diode will not get hot, the cost is low and the reliability is high.

Second aspect of embodiments

A controlling method of a power supply circuit of the first aspect of embodiments is provided in an embodiment. The same contents as those in the first aspect of embodiments are omitted.

Fig. 6 shows a flowchart of a controlling method 600 of the power supply circuit.

As shown in Fig. 6, the method 600 includes:

Block 601: a voltage convertor circuit converting an input voltage into an output voltage;

Block 602: a controller generating a controlling signal to control the switch unit;

Block 603: a voltage generator generating a voltage, and providing the voltage to a power supply terminal of the controller.

In the block 603, when the at least two rectifying diodes being normal, the voltage provided to the controller being an operating voltage of the controller, and the controller generates the controlling signal by being provided with the operating voltage. When one of the at least two rectifying diodes being open, the voltage provided to the controller being shutdown voltage, and the controller stops generating the controlling signal by being provided with the shutdown voltage.

As can be seen from the above embodiments, when one of the at least two rectifying diodes at the secondary side is open, the voltage in reverse direction will be provided to the power supply terminal of the controller, and the controller stops generating the controlling signal and the power supply circuit will stop work. Therefore, the rectifying diode will not get hot, the cost is low and the reliability is high.

Third aspect of embodiments

An electric equipment is provided in an embodiment. The electric equipment includes the power supply circuit according to the first aspect of embodiments.

In the embodiment, the power supply circuit is configured to convert an input voltage into an output voltage, according to a controlling signal, as described in the first aspect of embodiments. The output voltage may be provided to drive a lighting device connected to the terminals for the output voltage or to a driver to drive a lighting device, the lighting device may be LED.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A power supply circuit, comprising:

a voltage convertor circuit, configured to convert an input voltage into an output voltage, the voltage convertor circuit having a primary side and a secondary side, the primary side having at least one switch unit which controls the primary side to rectify the input voltage, the secondary side having at least two rectifying diodes, which being used to rectify voltage coupled from the primary side;

a controller, configured to generate a controlling signal to control the switch unit; and

a voltage generator, configured to be coupled to the primary side, being used to generate a voltage, and provide the voltage to a power supply terminal of the controller,

when the at least two rectifying diodes being normal, the voltage provided to the controller being an operating voltage of the controller, and the controller generates the controlling signal by being provided with the operating voltage;

when one of the at least two rectifying diodes being open, the voltage provided to the controller being shutdown voltage, and the controller stops generating the controlling signal by being provided with the shutdown voltage.
The power supply circuit according to claim 1, wherein,

the voltage generator comprises:

an auxiliary winding, arranged on the primary side, and arranged between a first node and a second node, the auxiliary winding couples to a primary winding of the primary side of the voltage convertor circuit;

a first diode (D32) , arranged in a first branch connecting the first node and the power supply terminal of the controller;

a second diode (D34) , arranged in a second branch connecting the first node and the power supply terminal of the controller; and

a Zener diode (Z31) , arranged in the second branch,

the operating voltage is provided through the first branch,

the shutdown voltage is provided through the second branch.
The power supply circuit according to claim 1, wherein,

the cathode of the second diode is coupled to the first node,

the anode of the second diode is coupled to the anode of the Zener diode.
The power supply circuit according to claim 1, wherein, the power supply circuit further comprises:

a resistor, arranged in series with the second diode and the Zener diode in the second branch.
The power supply circuit according to claim 1, wherein,

the anode of the first diode is coupled to the first node.
The power supply circuit according to claim 1, wherein,

the second node is coupled to a ground potential.
An electric equipment, comprising the power supply circuit according to one of claims 1-6.
A lighting device driver, comprising the power supply circuit according to one of claims 1-6.
A controlling method of a power supply circuit, the method comprising:

a voltage convertor circuit converting an input voltage into an output voltage, the voltage convertor circuit having a primary side and a secondary side, the primary side having at least one switch unit which controls the primary side to rectify the input voltage, the secondary side having at least two rectifying diodes, which being used to rectify voltage coupled from the primary side;

a controller generating a controlling signal to control the switch unit; and

a voltage generator generating a voltage, and providing the voltage to a power supply terminal of the controller, the voltage generator being configured to be coupled to the primary side,

when the at least two rectifying diodes being normal, the voltage provided to the controller being an operating voltage of the controller, and the controller generates the controlling signal by being provided with the operating voltage;

when one of the at least two rectifying diodes being open, the voltage provided to the controller being shutdown voltage, and the controller stops generating the controlling signal by being provided with the shutdown voltage.